GPS Time Synchronization Research Articles

Development of GPS time-based reference trajectories for quality assessment of multi-sensor systems

Abstract The development of multi-sensor systems (MSSs) goes hand in hand with assessing the quality of these complex systems. Therefore, reliable reference information of superior accuracy is essential for validation, serving as ground truth. When the assessment is based on 3D point cloud comparison, appropriate reference environments with suitable geometries are required. However, validation of an MSS can also be performed directly on its 3D position or even its 6D pose. This is particularly suitable for systems without sensors for environmental acquisition. When using kinematic measurement systems, the temporal relationship between the MSS and the reference trajectory must be considered, which can be challenging. Modern sensors of an MSS are often synchronized to GPS time. However, this global time information is not provided for high-accuracy tracking sensors such as robotic total stations (RTSs) or laser trackers (LTs). Instead, only a reference to an internal sensor time is implemented, which does not meet the highest quality requirements for reference trajectories. Depending on the motion speed, time offsets in the millisecond range can lead to significant trajectory inaccuracies. This paper presents investigations for GPS time synchronization of the polar measurement elements of both RTS and LT from Leica Geosystems. While the LT uses a precise trigger signal for the time link, the RTS requires the Measure & Stream application provided by the instrument manufacturer. The two different approaches are presented theoretically. Based on empirical long-term studies, their possibilities and limitations are critically discussed. For the high-frequency LT, reference trajectories with precise synchronization based on GPS time can be reliably realized. With an RTS, improved synchronization can be achieved by using Measure & Stream. Thus, 43 % lower tangential deviations from the reference could be achieved compared to the raw data. However, there are still inconstant time offsets of 63.9 ms on average. Depending on the speed of the target, this can lead to significant position deviations. Further investigations are required. In general, the developed approaches for the realization of GPS-synchronized reference trajectories can be used not only for the quality assessment of MSS, but also for monitoring or kinematic positioning applications.

A method for locating lightning strikes in distribution lines with multiple branches

A lightning strike fault location (FT) method for multi-terminal overhead lines based on 0-mode 1-mode wave velocity difference is proposed to address the shortcomings of current multi-terminal overhead line positioning methods that are difficult to identify due to multi-terminal GPS time synchronization and reflected traveling waves. Based on the wave velocity difference between 0-mode and 1-mode, single-end ranging is performed, and an FT judgment vector is formed based on the ratio of the ranging results of each monitoring terminal to the inherent length of the line. By analyzing the element features in the FT judgment vector, an FT criterion is proposed, and the FT results of the appropriate monitoring terminal are selected as the final FT. After PSCAD/EMTDC simulation verification, this method is suitable for complex multi-branch overhead lines, and can accurately locate the FT without being affected by time synchronization.

Wireless and Low-Power System for Synchronous and Real-Time Structural-Damage Assessment

The rise of Internet of Things (IoT) systems and the evolution of Low-Power Wide-Area Networks have directly contributed to the emergence of a new generation of Structural Health Monitoring (SHM) systems based on the Non-Destructive Test approach. Consequently, this article presents the design and development of a synchronous, low-cost, real-time, wireless, and low-power consumption SHM system for pre-existing buildings and infrastructures, which has been validated on a structure built in the High Middle Ages forming part of the historical heritage of the city of Seville (Spain). The system proposes a modular and scalable design with the capacity for synchronous monitoring of the accelerations of a structure thanks to the deployment of several reduced-size nodes that acquire and transmit the accelerations of the structures through a Secure Sockets Layer (SSL) NB-IoT connection. This aspect and Firmware Over The Air (FOTA) capability enables the permanent deployment of sensor nodes, thereby not only obviating the use of costly traditional devices but also granting access to the structures to be monitored for each test and maintenance task and hence supporting the tasks related to the preventive conservation of heritage. The experimental tests carried out demonstrate the low impact of GPS time synchronization and FOTA on the autonomy of the system. The precision of the system is also validated by comparing the results with a precision system in a real field test. Furthermore, continuous monitoring is guaranteed through the graphical interface developed as a composition of microservices, which enables management of the deployed networks.

ANALYSIS OF DEVICES AND SYSTEMS FOR MEASURING MUZZLE VELOCITY

The article analyzes instruments and systems for measuring the muzzle (initial) velocity of artillery and small arms ammunition of different calibers. Local and foreign devices that are mounted on weapons or which are located at a distance are given. Most of the devices considered in this article can work autonomously, which is an advantage when using them at the landfill.
 An important component of ensuring the defense capability of the State is the high level of Armed Forces of Ukraine equipment with new high-precision weapons and military equipment and the modernization of existing weapons, which involves verification of weapons samples for compliance with the declared characteristics of the manufacturer (supplier).
 The effectiveness of the tests depends on the accuracy and quality of the instruments(systems) which are used to measure the characteristics of the weapons. The initial speed of the ball (shell, mines, etc.) is one of the main characteristics of the weapon’s combat properties. It is determined experimentally and by additional calculations.
 The SL-520 series systems are versatile and precise instruments that allow the effective testing of weapons samples at training grounds. The advantages of these systems are: range of possible measurement speeds, high measurement accuracy, the possibility of measuring the muzzle velocity of all types of artillery and small-arms ammunition of different calibers, self-calibration option for the whole life cycle, integrated GPS time synchronization, the possibility of complex application of typical radars and the duration of autonomous operation.

Review of an Accurate System Utilizing GPS Technology

GPS provides precise position and control data anywhere on the planet and in any weather condition. GPS was originally intended for military usage, but in the 1980s, the US Department of Defense made it available for civilian use. The scientific applications of GPS in the military, community, and commercial sectors are expanding on a regular basis. Agriculture, construction, mining, measurement, package delivery, and logistical supply chain management all benefit from GPS technology. Precision GPS time synchronization is critical for big networks, navigation, finance systems, financial markets, and power grids. Wireless services are impossible to imagine without them. In this paper, we will go over the key aspects of GPS technology as well as a discussion of the systems that use it.

High-impedance fault location method of three-phase distribution lines based on electromagnetic time reversal

• Expanding the application scenario of the criterion of the minimum mirrored FCSE. • Accurately locating the single-phase HIF and identifying the fault phase. • Not affected by noise, GPS time synchronization, and the time delay of the device. • Location and diagnosis of single-phase HIF, phase to phase HIF, and three-phase HIF. Accurate location of high-resistance grounding faults in distribution lines is of great significance for improving the power supply reliability of power systems. In this study, a simulation model of a 10 kV three-phase distribution line is built using a numerical simulation platform. Further, a fault location method of three-phase distribution lines is proposed on the basis of the criterion of the minimum mirrored fault current signal energy (FCSE). The positioning accuracy of the high-impedance fault (HIF) is studied under different influencing factors. The results show that the proposed method can accurately locate the single-phase HIF of the three-phase distribution line, and the positioning error is within 50 m. However, it can only locate the fault when the fault resistance is 5 kΩ and below. In addition, the positioning accuracy of the proposed method for the HIF is not affected by noise and the sampling frequency, although the location accuracy under different fault inception angles is affected by fault resistance. Further, when the GPS time synchronization error is within 2 μs or the time delay of the transient signal device is within 2 ms, accurate positioning of the single-phase HIF can be realized. Moreover, by analyzing the three-phase FCSE distribution calculated in the reversed time, positioning and diagnosis of three HIF types, namely the single-phase grounding fault, phase-to-phase fault, and three-phase grounding fault, can be realized. Finally, fault phase identification of the single-phase HIF can also be achieved.

Innovative seismic imaging of volcanogenic massive sulfide deposits, Neves-Corvo, Portugal — Part 2: Surface array

Seismic methods are an affordable and effective way of studying the subsurface for mineral exploration. With the goal of testing new technologies for mineral exploration in highly challenging mining areas, in early 2019, an innovative seismic survey was conducted at the Neves-Corvo mine, south Portugal. We have focused on the data and results from the surface array data, whereas other work deals with the underground seismic data. The surface seismic survey consisted of two perpendicular 2D profiles positioned above the known world-class tier-1 Lombador deposit. Simultaneously, a survey inside the active underground mine took place, being unique because it included the testing of a prototype system that enabled accurate GPS-time (microsecond accuracy) synchronization inside the mine tunnels, approximately 650 m below the surface profiles. Due to the active mining operations, the surface data are noisy. To handle this, a carefully tailored processing algorithm was developed and applied to enhance reflections in the data, interpreted to originate from lithologic contacts and the Lombador deposit. The results and interpretations from 2D processing were validated taking advantage of the known deposit geometry using 3D exploding reflector modeling and pseudo-3D cross-dip analysis. These analyses suggest that there is an out-of-plane signature of the Lombador deposit on the surface data. Additionally, source points activated in the exploration tunnels and simultaneously recorded on the surface profiles allowed for the creation of a 2D velocity model that was used for migration and time-to-depth conversion, providing a reliable 2D seismic section of the subsurface under the surface profiles. We determine that limited surface coverage 2D surveys and a velocity model derived from the tunnel-to-surface seismic recordings allow for imaging of key subsurface geologic structures and delineating mineral deposits of economic interest.

Optimal Placement of Synchronized Voltage Traveling Wave Sensors in a Radial Distribution Network

A transmission line fault generates transient high frequency travelling waves (TWs) that propagate through the entire network. The fault location can be determined by recording the instants at which the incident waves arrive at various points in the network. In single end-based methods, the incident wave arrival time and its subsequent reflections from the fault point are used to identify the fault location. In heavily branched distribution networks, the magnitude of the traveling wave declines rapidly as it passes through multiple junctions that cause reflection and refraction to the signal. Therefore, detecting the first incident wave from a high impedance fault is a significant challenge in the electrical distribution networks, in particular, subsequent reflections from a temporarily fault may not be possible. Therefore, to identify a high impedance or temporary faults in a distribution network with many branches, loads, switching devices and distributed transformers, multiple observers are required to observe the entire network. A fully observable and locatable network requires at least one observer per branch or spur which is not a cost effective solution. This paper proposes a reasonable number of relatively low-cost voltage TW observers with GPS time-synchronization and radio communication to detect and timestamp the TW arrival at several points in the network. In this regard, a method to optimally place a given number of TW detectors to maximize the network observability and locatability is presented. Results show the robustness of the proposed method to detect high impedance and intermittent faults within distribution networks with a minimum number of observers.

TravellingWave Fault Location System based on IEC61850

Travelling wave fault location (TWFL) system has been matured in recent years due primarily to the availability of high speed sampling techniques, fast communications technology and GPS time synchronization. However, it has not yet been fully integrated into the digital substation based on IEC61850 standard. Proposal for modeling the TWFL system by the IEC61850 standard has already been proposed in another paper. This paper focuses on the communication requirements of the TWFL system in a digital substation, both at the station level and the process level. The application of GOOSE messages and the need for high speed sampling merging unit are discussed. The paper also reports on the latest research into the electronic transformer technology which can satisfy the high speed sampling requirements of TWFL.

Research and implementation of substation clock unsynchrony alarm system based on GPS pulse

In order to change the status quo within the substation bay control devices which only passive receiving IRIG-B GPS clock code or PPS, for the purpose of the research and the realization method of substation clock unsynchrony alarm system based on GPS pulse. On the basis of existing substation SCADA system and GPS time synchronization system, this paper realizes the real-time monitoring of time synchronization of substation bay control devices by simple modification and introduction of simple algorithm. This paper describes in detail the system construction method and relative time difference algorithm, as well as the project implementation method, to achieve the correct and punctual on-line monitoring of the bay control device, effective control of substation accidents caused by device time unsynchrony, greatly improving the stability of substation operation.

Study on Unified Reference Source Phase-Check Technology Based on Synchronized Phasor Measurement

In the power system, the phase-check is a simple but very important work. The newly built, transformed and expanded power plant, transformer substation electrical equipment and power transmission lines before put into operation must be carried out phase-check test, in order to ensure voltage phase sequence and phase correct. At present, there are some limitations of traditional phase-check technology in China. In this paper, we study the method of unified reference source based on synchronized phasor measurement technology. Through the GPS time synchronization signal to realize synchronous sampling of source voltage signal in different regions, by comparing to the phase of a fixed reference source signal in the power network to determine the phase relationship between any two different power points, and thus to complete the work of phase-check. The unified reference source phase-check method based on the synchronized phasor measurement technique is simple, easy to operate, and has high efficiency, which has unique advantages. And wide area power grid phase-check can be realized.

Overview of data acquisition and central control system of steady state superconducting Tokamak (SST-1)

Steady State Superconducting Tokamak (SST-1) has been commissioned successfully and has been carrying out limiter assisted ohmic plasma experiments since the beginning of 2014 achieving a maximum plasma current of 75kA at a central field of 1.5T and the plasma duration ∼500ms. In near future, SST-1 looks forward to carrying out elongated plasma experiments and stretching plasma pulses beyond 1s. The data acquisition and central control system (CCS) for SST-1 are distributed, modular, hierarchical and scalable in nature The CCS has been indigenously designed, developed, implemented, tested and validated for the operation of SST-1. The CCS has been built using well proven technologies like Redhat Linux, vxWorks RTOS for deterministic control, FPGA based hardware implementation, Ethernet, fiber optics backbone for network, DSP for real-time computation & Reflective memory for high-speed data transfer etc.CCS in SST-1 controls & monitors various heterogeneous SST-1 subsystems dispersed in the same campus. The CCS consists of machine control system, basic plasma control system, GPS time synchronization system, storage area network (SAN) for centralize data storage, SST-1 networking system, real-time networks, SST-1 control room infrastructure and many other supportive systems. Machine Control System (MCS) is a multithreaded event driven system running on Linux based servers, where each thread of the software communicates to a unique subsystem for monitoring and control from SST-1 central control room through network programming. The CCS hardware and software architecture is capable to fulfill the present operation and control requirement of SST-1. The CCS is successfully validated in several operation campaigns of SST-1 since year 2013.The lossless PXI based data acquisition of SST-1 is capable of acquiring around 130 channels of the ranging from 10KHz to 1MHz sampling frequency and is capable to acquire the volume of 500Mbytes of data in each shot. The indigenously developed Matlab based software utility is being used to analyze the data. The complete system is also validated in several operation campaigns of SST-1 since year 2013.This paper will provide the overview of all the above mentioned subsystems of SST-1 DAQ and SST-1 CCS focusing on the design, architecture, performance, lesson learned and future upgrade plans.

The Testing of MLAT Method Application by means of Usage low-cost ADS-B Receivers

<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-fareast-font-family: 'MS Mincho'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;" lang="EN-US">The paper describes the process and results achieved during the measurement which was realized with the aim of identify an applicability of MLAT (Multilateration) method by means of using so-called “low-cost” ADS-B receivers. In terms of measurement, ADS-B receivers without GPS time synchronization module was utilized thus specific time synchronization method was required to implement.</span>

北斗主导多模系统在广域电能质量与能效分析方面的应用

现代电力系统结构日趋复杂，现代电网的安全性存在新的挑战，电网的广域电能质量实时监控将越来越重要。现阶段电网主要依赖美国的GPS来完成。但GPS的时间同步精度和定位精度受美国限制，因此可靠性低、自主性差。基于安全性考虑，有必要对基于我国北斗卫星导航系统为主，兼容多种导航模式的北斗主导多模系统进行研究。本文详细分析了利用北斗主导多模系统的高精度授时系统如何提高电能质量监测水平和能效分析可靠性，并通过对比仿真实验验证了北斗主导多模系统的可行性。 Modern power system structure is increasingly complicated, and there exists new challenges about the security of modern power grid, so the grid wide-area real-time monitoring of power quality will be more and more important. At the present stage grid mainly depends on the GPS to complete this task. But the GPS time synchronization accuracy and positioning precision is restricted by the United States, so the reliability is low and autonomy is poor. Based on security considerations, it is necessary to study Beidou dominating multimode system in which China’s Beidou satellite navigation system is given priority to and it is compatible with a variety of navigation modes. This report analyzes the application of synchronous phasor measurement unit (PMU) in detail, and verifies that the application of new system can improve the measuring accuracy.

Measurements of the orthogonal magnetic components of the pulse component of infralow and very low electromagnetic fields at svalbard

A complex of equipment for recording three components Hx, Hy, and Hz of the pulse component of an electromagnetic field in the range of infralow-very low frequencies, which is incorporated in the geophysical observatory of the Polar Geophysical Institute (Barentzburg, Spitsbergen archipelago), is described. The complex operates under the control of the Linux operational system and is integrated in the local observatory computer network, thus providing both the remote access to data and the GPS time synchronization. The use of buffer transformers in both the signal circuit and the circuit for connection to the collective observatory supply line made it possible to improve the electromagnetic compatibility of this complex with the main instruments of the observatory. The technique for conducting the absolute calibration of the equipment is described.

Vehicle teleoperation using 3D maps and GPS time synchronization.

In conventional vehicle teleoperation systems, using low-bandwidth, high-delay transmission links causes a serious problem for remote control of the vehicles. To solve this problem, a proposed teleoperation system employs 3D maps and GPS time synchronization. Two GPS receivers measure the transmission delay, which the system uses to estimate the vehicle's location and orientation. Field experiments show that the 3D-map-based interface lets users easily comprehend the remote environment while navigating a vehicle. The experiments also show that taking communication delays into account improves maneuverability.

Localization with sparse acoustic sensor network using UAVs as information-seeking data mules

We propose and demonstrate a novel architecture for on-the-fly inference while collecting data from sparse sensor networks. In particular, we consider source localization using acoustic sensors dispersed over a large area, with the individual sensors located too far apart for direct connectivity. An Unmanned Aerial Vehicle (UAV) is employed for collecting sensor data, with the UAV route adaptively adjusted based on data from sensors already visited, in order to minimize the time to localize events of interest. The UAV therefore acts as a information-seeking data mule, not only providing connectivity, but also making Bayesian inferences from the data gathered in order to guide its future actions. The system we demonstrate has a modular architecture, comprising efficient algorithms for acoustic signal processing, routing the UAV to the sensors, and source localization. We report on extensive field tests which not only demonstrate the effectiveness of our general approach, but also yield specific practical insights into GPS time synchronization and localization accuracy, acoustic signal and channel characteristics, and the effects of environmental phenomena.

Measurement system design and implementation for grid-connected marine substation

A marine substation for a grid-connected wave power plant has been designed and constructed at Uppsala University. The measurement system for the substation has been developed from basics, and the procedure is described in this article. Subsea electrical installations set high constraints on the control and data acquisition systems used, and traditional GSM networks and GPS time synchronization are difficult and inefficient. These circumstances exclude many well-proven methods to be utilized. A compactRIO-based system, with integrated real-time controller and Field-Programmable Gate Array chip, is chosen as most suitable for this task. The system is designed to meet the special requirements encountered in this unusual application, including large data sampling, grid connection control and protection systems. The system is communicating to shore via a subsea copper cable and single-pair high-speed digital subscriber line modems. The design was successful and full-fills all the system requirements. The aim of the article is to provide future researchers with a good design and implementation procedure for setting up large measurement systems.

Energy-2M generating-measuring complex of directional operation for seismic monitoring and sounding of ore objects

A generating-measuring complex of directional operation, which allows investigating seismically dangerous zone of stressedly-deformed state of rock, ore zones, and fracture zones in the directions which are the most sensitive from the standpoint of the aim in view, namely along and across the strike axes of the object of interest, is developed. The complex includes the Energy-2M directional operation generator and a portable high-sensitivity KVVN-7m measuring station that allows performing frequency probing with controllable sources and sounding in the field of natural electromagnetic field variations during one cycle. The generator includes a system of independent phase and amplitude adjustment of the current at the output of the Energy-2M generator inverter along two channels. A circuit of programmed generator current supply to two mutually orthogonal antenna arrays (long grounded lines) and a system of precision control over the current parameters in each arm is developed. The generator allows generating a programmed current with circular or elliptical field polarization in the vicinity of the object under study in the specified direction in the frequency range from 1 to 2000 Hz. The Energy-2M generator is mounted on board a ZIL-131 motor vehicle and fed by two PN-72 generators 15 kW each. The KVVN-7 digital measuring station has been completely modified. Moreover, all out-of-date elements have been replaced by modern operational amplifiers characterized by extremely low internal noises, which do not exceed unities or tenths of nV/Hz0.5. The generating complex is equipped with a system for control, regulation, protection, and automation (SCRPA) based on GPS time synchronization. Thermostatting of the unit for clock frequency and reference voltage is provided. All these measures allowed reaching the accuracy of synchronization over the absolute time not worse than 2 × 10−4 s, and frequency stability of the generator signal not worse than 10−7 Hz.

Design of a Wireless Multi-Radio-Frequency Channels Inspection System for Bridges

This paper presents a wireless multi-radio-frequency channels inspection system (WMCIS) based on wireless sensor networks (WSN) for the sake of bridge structural vibration inspection. The designed system consists of a wireless controller and eight wireless nodes with acceleration sensing units. The whole system has 64 collection channels, so every wireless node has eight 24-bit A/D channels. Integrated with acceleration sensing units, an embedded low-power microprocessing unit, a wireless transceiver unit, a large-capacity power unit, and a GPS time synchronization unit, the wireless node has the functions such as data collection, initial analysis, data storage, and wireless data transmission. The wireless controller, equipped with a high-performance computation unit, a wireless transceiver unit, a mobile power source, and an embedded data analysis software, can totally control multiple wireless nodes and receive and analyze data for parameter identification. To verify the performance of the WMCIS, experiments are made on the Caihong Bridge and Jinzhou Bridge in China for inspecting the bridge structural vibration. Experimental results show that the system has the advantages such as fast arrangement, high sampling rate, high resolution, capacity of low-frequency inspection, and GPS clock project for time synchronization and, thus, has good application prospects and practical value.